Design, synthesis and structure-activity relationship studies of novel macrocyclic 2,4-diaminopyrimidines as HPK1...

Hematopoietic progenitor kinase 1 (HPK1) functions as a key negative regulator of T cell receptor signaling and has been considered a potential target for cancer immunotherapy. Despite great progress in developing HPK1 inhibitors, no small-molecule inhibitors have been approved for cancer treatment to date. Herein, we describe the design and synthesis of a novel series of macrocyclic 2,4-diaminopyrimidine derivatives as HPK1 inhibitors. Among these, the representative compound 21 exhibited potent HPK1 inhibition with an IC₅₀ value of 1.0 nM in an ADP-Glo assay. Furthermore, compound 21 effectively inhibited phosphorylation of the downstream adaptor protein SLP76 and enhanced IL-2 secretion in human Jurkat T cells. Taken together, this study further validates macrocyclization as an effective strategy for designing HPK1 inhibitors with innovative scaffolds and offers compound 21 as a structurally novel lead compound for the development of HPK1 inhibitors.